Printing machines using transport chains are known; see, for example, German Patent Disclosure Document DE-OS No. 30 15 519. The printing machine there shown has an endless chain transport conveyor and a cylinder located between the supply and return runs. This printing cylinder is formed with a rubber surface, that is, as a rubber cylinder and a plate cylinder in engagement with the printing cylinder, which further includes an inker and a damper. Theoretically, the possibility arises to use such a printing system to apply lacquer, or other coatings, or impression printing, or to apply with such a cylinder a liquid which prevents smear of ink, for example by setting or hardening printing ink applied on the upper side of a printed sheet. It is not necessary to construct a complete offset printing system if it is only required to apply a liquid, such as lacquer or other coating to the sheet. Simplification of the system, however, is difficult, since the gripper elements which transport the sheet, can fit within the groove of the blanket cylinder only to the extent of tangential relationship of the gripper surfaces with respect to the circumference of the rubber cylinder.
The grippers, customarily, are carried by a cross bar which extends between two chains forming the transport conveyor, one at either axial end of the cylinders. If the gripper cross bar engages deeper into the groove of the cylinder the sheet is bent about the edge of the groove and may be creased thereby; further, registration difficulties and alignment difficulties may result. An impression, or partial coating of the sheet thus would not occur at the proper position thereof. The required position of the gripper cross piece can be obtained by suitable dimensioning of the groove. In the position in which the gripper surfaces which actually grip the sheet are tangent with the circumference of the cylinder, results, however, in components of the gripper to extend over the outer circumference thereof. This occurs in the forward run as well as in the reverse run of the conveyor chain. If another printing cylinder is located at the sides of the rubber blanket cylinders which are engaged by the transport chain, then no difficulties will result since the printing cylinders, themselves, also have grooves which can receive the projecting portions of the gripper structure attached to the chain. It is not, however, possible to apply application rollers rather than a plate cylinder which has grooves, for example application rollers of diameter which is different, typically smaller than the blanket cylinder there against, since danger would result that such application rollers collide with projecting portions of the gripper structure.
The machine, thus, is generally directed to a printed machine system which has transport chains, typically two chains, one at each axial end of the respective printing cylinders with cross elements or cross braces which carry the gripper structures themselves, and which convey sheets from a printing station to another apparatus, for example a stacking apparatus. The return run of the chain runs freely, that is, empty. Apparatus is provided to apply a liquid at least to the upper side of the sheet being conveyed by the chain, which includes, for example, an application roller running against the blanket cylinder which has a groove capable of receiving the gripper structures, including, for example, the cross pieces or cross elements connecting the chains and holding the grippers themselves.